This invention relates to a signal device for a pneumatic tire and particularly to a signalling cap for the inflating valve of a pneumatic tire which has an electrical sound producing unit for the purpose of alarming when the tire is deflated to a pressure below a predetermined proper pressure.
Signal devices for pneumatic tires are known in the art. Some of them are of the type which is used during inflation of the tire for the purpose of alarming when the pressure in the tire exceeds a predetermined required pressure. Some of them are used as a cap for the inflating valve of a tire as well as a signal device to signal when the pressure in the tire is seriously deflated. U.S. Pat. No. 2,334,095 discloses a signal device of the latter type which includes a cap-like casing in which is mounted a valve that permit air to enter the casing from the tire to which the casing is connected when the tire is deflated to a predetermined pressure. The casing also contains a sound making unit which has an air-tight hood member that explodes when air enters the casing. U.S. Pat. No. 1,626,294 discloses a signal device which is mounted on the inflating valve of a tire after the tire is inflated and which includes a spring loaded thimble to be used as an indicator to show the deflated pressure in the tire.